linux-kernel - [RFC PATCH 2/2] 9p: retrieve fid from file if it exists when getattr.

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Date:   Mon, 20 Jul 2020 09:46:22 +0800
From:   Jianyong Wu <jianyong.wu@....com>
To:     ericvh@...il.com, hch@....de, dhowells@...hat.com,
        lucho@...kov.net, asmadeus@...ewreck.org
Cc:     v9fs-developer@...ts.sourceforge.net, linux-kernel@...r.kernel.org,
        Kaly.Xin@....com, justin.he@....com, jianyong.wu@....com,
        wei.chen@....com
Subject: [RFC PATCH 2/2] 9p: retrieve fid from file if it exists when getattr.

fid should be retrieved from file when it is not NULL in getattr.
it denotes that getattr is called by fdstat from userspace when
file is exist, which means we should get info from file context
not dentry to avoid the failure when the dentry has gone.

Signed-off-by: Jianyong Wu <jianyong.wu@....com>
---
 fs/9p/vfs_inode.c      | 9 +++++++--
 fs/9p/vfs_inode_dotl.c | 9 +++++++--
 2 files changed, 14 insertions(+), 4 deletions(-)

diff --git a/fs/9p/vfs_inode.c b/fs/9p/vfs_inode.c
index c9255d399917..f562f5710eae 100644
--- a/fs/9p/vfs_inode.c
+++ b/fs/9p/vfs_inode.c
@@ -1054,7 +1054,7 @@ v9fs_vfs_getattr(const struct path *path, struct kstat *stat,
 {
 	struct dentry *dentry = path->dentry;
 	struct v9fs_session_info *v9ses;
-	struct p9_fid *fid;
+	struct p9_fid *fid = NULL;
 	struct p9_wstat *st;
 
 	p9_debug(P9_DEBUG_VFS, "dentry: %p\n", dentry);
@@ -1063,7 +1063,12 @@ v9fs_vfs_getattr(const struct path *path, struct kstat *stat,
 		generic_fillattr(d_inode(dentry), stat);
 		return 0;
 	}
-	fid = v9fs_fid_lookup(dentry);
+	if (stat->filp) {
+		fid = stat->filp->private_data;
+		WARN_ON(!fid);
+	}
+	if (!fid)
+		fid = v9fs_fid_lookup(dentry);
 	if (IS_ERR(fid))
 		return PTR_ERR(fid);
 
diff --git a/fs/9p/vfs_inode_dotl.c b/fs/9p/vfs_inode_dotl.c
index 60328b21c5fb..6b7cbe74b0bb 100644
--- a/fs/9p/vfs_inode_dotl.c
+++ b/fs/9p/vfs_inode_dotl.c
@@ -460,7 +460,7 @@ v9fs_vfs_getattr_dotl(const struct path *path, struct kstat *stat,
 {
 	struct dentry *dentry = path->dentry;
 	struct v9fs_session_info *v9ses;
-	struct p9_fid *fid;
+	struct p9_fid *fid = NULL;
 	struct p9_stat_dotl *st;
 
 	p9_debug(P9_DEBUG_VFS, "dentry: %p\n", dentry);
@@ -469,7 +469,12 @@ v9fs_vfs_getattr_dotl(const struct path *path, struct kstat *stat,
 		generic_fillattr(d_inode(dentry), stat);
 		return 0;
 	}
-	fid = v9fs_fid_lookup(dentry);
+	if (stat->filp) {
+		fid = stat->filp->private_data;
+		WARN_ON(!fid);
+	}
+	if (!fid)
+		fid = v9fs_fid_lookup(dentry);
 	if (IS_ERR(fid))
 		return PTR_ERR(fid);
 
-- 
2.17.1